Process of dehydrating nitrocellulose and reducing the fire risk thereof



- Io Drawing.

pasted s... I f t UNITED ST T a 1,552,807- "PATENT OFFICE.

. name 1:. ms or nocnns'rna, NEW YORK. assmnon 'ro mm xonax comm, 0 mm,naw YORK, a conrona rron or NEW YORK.

mam or nmnaa'rma nnnocmwnosn AND minucme 1m 313x- To all whom'it mayconcern: I

I Be it known that 1, JAMES HMHASTE, a citizen of the United States ofAmerica, residin at Rochester, in the county of Monroe and tate of NewYork, have invented certain new and useful Im rovements in Proc= essesof DehydratingNitrocellulose and Reducing the Fire Risk Thereof, ofwhich the followingis a full, clear, and exact specification. I

This invention .relates to the artof handling nitrocellulose between thewashing operations and the plasticizing operations. One object of theinvention is to provide process steps by which all-harmful amounts ofwater may be removed from the washed nitrocellulose fibers withoutincreasing the fire risk, such fibers being kept in a condition ofcomparativesafety up to the time when they are incorporated intosuitable compositions or do es.

Another object 0 the invention is to substantially dehydrate thenitrocellulose by the use of one liquid and then wholly or partiallyreplace such liquid by a second one which is capable of loweringlthefire risk, and can, if desired, enter the ingredient along with thenitrocellulose. Another object is to mediate product intie form ofnitrocellulose fibers suitably protected against fire risk and capableof being readily stored and transported. Other objects will hereinafterappear.

-When cellulose fibers have been nitrated, the acid isremoved therefromby thorough washing in water or aqueous solutions. But the amount ofwater which remains in the mass of washed fibers cannot be reduced bywringing or like mechanical means to a oint where the nitrocellulose isready for incorporation into the usual plastic compositions. If thisresidual moisture be finally removed by evaporation, the nitrocellulosefibers become so dry that the hazard of fire, or even of explosion, isvery greatly increased, as experience has shown. In order that thenitrocellulose may be stored and transported safely, it should be ke tin a wetted condition, the term wetted ere being intended to apply tofibers that are inter mingled with non-aqueous liquids as well as whenwetted with water.

It been cust m y to remo e th al composition as an rovide a novel inter-THEREOF.

Application mam 1, 1021.' Serial m. 451,720. v

water, left after the wringing operation, by percolat ng a suitableliquid through the mass of fibers, the removal of the water taking placeby mere displacement or absor'ption. in the removing liquid, or by bothmethods acting simultaneously. After the fibers have been thusdehydrated, they are leftin the condition in which they are wetted bythe water-removing liquid. This remainmg liquid has been depended uponto keep down the fire risk of the fibers by preventing them frombecoming dry, and has customarily entered into the final composi tionsor dopes as an ingredient thereof along with the nitrocellulose.

Now the'substances'which-act as water removers and at the same time arecapable of lowering the fire'ri'sk and entering nto the final com sitionare comparatively'few'and several 0 them are very expensive. I havediscovered that the-range of liquid sub- 7 I stances suitable for usecan be greatly in creased and the expense moreover diminished bydlvlding the Intermediate part of the process into two ste s wherein twodilferent liquids are employe In this wa each liquid does not have tohave all of t e properties that have heretofore been considerednecessary, buteach liquid supplements the other so that all of thenecessary effects are produced in the (process at the proper time.

The li uid use in the first or dehydrating ste of t e process may be onethat is not desired in the final composition or dope and may 'inaddition not be well adapted .for the lowering of the fire risk. Yet itmay be cheap and well adapted for the removal of the water. It should,of course, be a non-solvent of nitrocellulose under the conditions inwhich itis'used, the nitrocellulose fibers maintaining their essentialcon-. dition without gummin up into a sticky mass or solution. Thediquid should also, of course, be substantially inert toward thenitrocellulose durin contact therewith, t at is, it should notinjuriously re-act chemically with the fibers the time that it is indisadvantage, bcause the second step of my rocess may take place beforethe fibers have dried to a dangerous extent. The water removing ordehydrating action is carried, in the preferred form of my invention,

- still wet with the residue of the dehydrating liquid of the firststep. The first liquid is wholly or partially (preferably the-former)replaced by a second liquid which is adapted to lower the firerisk andenter into the final composition as an ingredient thereof. Preferably itis of low volatility, so that the fibers remain wetted with it overconsiderable periods of time and thus do not become .dangerously dryduring storage and trans-' portation. It is, of course, substantially anon-solvent of nitrocellulose under the conditions of this part of theprocess and is likewise practically inert toward the fibers.

.It is desirable that it be of low combustibility and it is beneficialif it does not tend to take up moisture from the airto a harmful extent.It should likewise be sufliciently free from mineral matter,particularly when transparent film is to be roduced. There are a largenumber of single liquid substances, or liquids which may be mixed witheach other or with suitable, solids, that have the characteristicsdesired for the sec- 0nd step of my process. I find thatmonochlornaphthalene is satisfactory for this 0 eration. I may use thecommercial form 0? this substance which is an almost colorless oilyliquid containing small amounts of more highly chlorinated derivatives.It boils between 240 C. and 290 C.

The treatment with the dehydrating liquid and the subsequent whole orpartial displacement of the latter by the fire-riskreducing ingredientmay be performed by percolating the liquids through the mass,

the excess being removed mechanically. .It is convenient to placewater-carrying nitrocellulose in a centrifuge and tospray the formerwith ethyl alcohol while the apparatus is running until the desireddegree of dehydration is obtained. The monochlornaphthalene may also beapplied to the nitrocellulose in the centrifuge until the alcohol isdisplaced to the desired extent. If the monochlornaphthalene' or othersuitable liquid for the second step slightly absorbs in the liquid ofthe first step, it may facilitate the creeping of the second liquidalong the fibers of the nitrocellulose, so as Any excess of the liquidis wrung out.

The nitrocellulose fibers coated or intermingled with themonochlorn'aphthalene or other suitable second liquid ingredientconstitute a useful intermediate product which can be readily stored andtransported with com arative safety and finally can be .to uniformly wetthem throughout the mass.

wor ed up into the known compositions in t this modification the rangeof substances,

which may be used in the second step, is I not as large as in thepreferred form, but a substance suitable for entering the final"composition may be employed which has muchless dehydrating propertiesthan would be necessary ifit were not merely supplementing the firstdehydrating action.

The liquid, which removes the water in the first step, can be usedrepeatedly, after dehydration, when necessary, in the usual way. Anyexcess of the second liquid can be used again, after purification ifdesired.

By wayof further illustration, propyl and iso ropyl alcohol can likewisebe used in the rst step, alone or mixed with ethyl alcohol, and in thesecond step monochlorbenzol, tricresyl phosphate, toluol and xylol maybe employed. It will be noted that these, as well asmonochlornaphthalene, are substantially anhydrous, that is they do notbring in undesirable amounts of moisture into the mass or the finalcompositions. They are likewise substantially non-solvents by themselvesat room temperature.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patents is:

1. The process of dehydratin nitrocellulose and reducing the fire risk tereof prior to compounding a composition thereof,

which comprises treating washed nitrocellulose carrying water with awater-removing liquid which is substantially anon-solvent ofnitrocellulose and then treating the nitrocellulose with a difi'erentliquid which is substantially a non-solvent by itself of nitrocelluloseat room temperature and is adapted to enter said nitrocellulosecomposition as an ingredient thereof.

2. The process of dehydratin nitrocellulose and reducing the fire risk tereof prior to compounding a composition thereof,

which comprises treating washed nitrocellulose carrying water, with awater-absorbing liquid which is substantially a non-solvent ofnitrocellulose and is substantially inert to the latter, and thentreating the nitrocellulose with a different liquid which is anon-solvent by itself of nitrocellulose at room temperature, issubstantially inert to: ward the latter and is adapted to enter saidnitrocellulose composition as an ingredient thereof.

3. The process of dehydrating nitrocellulose and reducing the fire riskthereof prior to compounding a composition thereof, which comprisestreating washed nitrocellulose carrying water with a. water-absorbingliquid which is substantially a non-solvent of nitrocellulose and thentreating the nitrocellulose with a different liquid Which is by itselfsubstantially a non-solvent thereof at room temperature, issubstantially free from mineral matter and is adapted to enter saidnitrocellulose composition as an ingredient thereof.

4. The process of dehydrating nitrocellulose and reducing the fire riskthereof prior to compounding a composition thereof, which comprisestreatingwashed nitrocellulose carrying water with a water-removingliquid which is substantially a nonssolvent of nitrocellulose and thentreating the nitrocellulose with a different liquid which is by itselfsubstantially a non-solvent thereof at room temperature and is of lowvolatility,

said second named liquid being adapted toenter said composition asaningredient thereof.

5; The process of dehydrating nitrocellulose and reducingthe fire riskthereof prior to compounding a composition thereof, which comprisestreating washed nitrocellulose carrying water with ethyl alcohol andthen treating .the nitrocellulose with a diflose carrying water witferent li uid which is by itself substantially a non-so vent thereof atroom temperature and is of low volatility, said liquid being adapted toenter said composition as an ingredientthereof. I

6. The process of dehydrating nitrocellulose and reducing the fire riskthereof, which comprises treating1 washed nitrocellua water-removingliquid which is substantially a non-solvent of nitrocellulose and thentreating the nitrocellulose with a substantially anhydrous organicliquid which is by itself substantially a non-solvent thereof at roomtemperature, is chemically inert with respect thereto, and is oflowinflammability.

7. The process of dehydrating nitrocellulose and reducing the fire riskthereof prior to compounding a composition thereof, which comprisestreating washed nitrocellulose carrying water with a water-removingliquid which is substantially a non-solvent 0f nitrocellulose, and thentreating the nitrocellulose with a different liquid which by itself issubstantially a non-solventthereof at room temperature and is of lowvolatility, said second named 'liquid' being adapted to enter saidcomposition as an ingredient thereof and being of low inflammability.

8. The'process of dehydrating nitrocellulose and reducing the fire riskthereof, which comprises treating washed nitrocellulose carrying waterwith ethyl alcohol to remove water therefrom, and then treating ilahenitrocellulose with monochlornaphthaene.

day of March 1921. 7

JAMES H. HASTE.

Signed at Rochester, New York, this 26th

